Lens system

ABSTRACT

Compact narrow angle lens systems that may be used in small form factor cameras. The lens system may include six lens elements with refractive power, and may provide lower F-numbers while maintaining or improving imaging quality and package size when compared to other compact lens systems. Total track length of the lens system may be 6.5 millimeters or less, for example 5.9 or 6 millimeters. Focal length of the lens system may be 7.0 millimeters or less, for example 6.6 millimeters. The lens system may include an aperture stop located behind the front vertex of the lens system, for example between the first and second lens elements, that effectively moves the ideal principal point of the camera to in front of the front vertex. The lens system may provide a focal ratio of 2.8 or less, for example 2.6 or 2.4.

PRIORITY INFORMATION

This application is a continuation of U.S. patent application Ser. No.15/285,898, filed Oct. 5, 2016, which claims benefit of priority of U.S.Provisional Application Ser. No. 62/245,196 entitled “LENS SYSTEM” filedOct. 22, 2015, which are hereby incorporated by reference herein intheir entirety.

BACKGROUND Technical Field

This disclosure relates generally to camera systems, and morespecifically to high-resolution, small form factor camera systems andlens systems.

Description of the Related Art

The advent of small, mobile multipurpose devices such as smartphones andtablet or pad devices has resulted in a need for high-resolution, smallform factor cameras for integration in the devices. However, due tolimitations of conventional camera technology, conventional smallcameras used in such devices tend to capture images at lower resolutionsand/or with lower image quality than can be achieved with larger, higherquality cameras. Achieving higher resolution with small package sizecameras generally requires use of a photosensor with small pixel sizeand a good, compact imaging lens system. Advances in technology haveachieved reduction of the pixel size in photosensors. However, asphotosensors become more compact and powerful, demand for compactimaging lens system with improved imaging quality performance hasincreased.

SUMMARY OF EMBODIMENTS

Embodiments of the present disclosure may provide a high-resolutionnarrow angle camera in a small package size. A camera is described thatincludes a photosensor and a compact lens system. Embodiments of acompact lens system with six lens elements are described that mayprovide a larger image and with longer effective focal length than hasbeen realized in conventional small form factor cameras. Embodiments ofthe camera may be implemented in a small package size while stillcapturing sharp, high-resolution images, making embodiments of thecamera suitable for use in small and/or mobile multipurpose devices suchas cell phones, smartphones, pad or tablet computing devices, laptop,netbook, notebook, subnotebook, and ultrabook computers. In someembodiments, a narrow-angle camera as described herein may be includedin a device along with one or more other cameras such as a conventional,wider-field small format camera, which would for example allow the userto select between the different camera formats (e.g., telephoto orwide-field) when capturing images with the device. In some embodiments,two or more narrow-angle cameras as described herein may be included ina device, for example as front-facing and rear-facing cameras in amobile device.

In some embodiments, the narrow angle lens system may be a fixed lenssystem configured such that the effective focal length f of the lenssystem of 7 millimeters (mm) or less (e.g., within a range of 6.0-7.0mm), the F-number (focal ratio) is 2.8 mm or less (e.g., within a rangefrom about 2.2 to about 2.8), and the total track length (TTL) of thelens system is 6.5 mm or less (e.g., within a range of about 5.5 toabout 6.5 mm). In the example embodiments described herein, the lenssystem may be configured such that the effective focal length f of thelens system is at or about 6.6, and the F-number is at or about 2.4 or2.6. However, note that the focal length and/or other lens systemparameters may be scaled or adjusted to meet specifications of optical,imaging, and/or packaging constraints for other camera systemapplications.

In some embodiments, the location of the aperture stop may be movedbehind the front vertex of the lens system, for example behind the frontvertex at the first lens element or between the first and second lenselements. Moving the aperture stop inwards (towards the image side)effectively moves the ideal principal point of the camera forwards, tothe object side and in front of the front vertex of the lens system.

In some embodiments, the narrow angle lens system may be adjustable. Forexample, the lens system may be equipped with an adjustable iris oraperture stop. Using an adjustable aperture stop, the F-number may bedynamically varied within some range, for example within the range of2.2 to 10. In some embodiments, the lens system may be used at fasterfocal ratios (<2.4), possibly with degraded imaging quality performance,at the same field of view (FOV, e.g. 36 degrees), or with reasonablygood performance at a smaller FOV.

The refractive lens elements in the various embodiments may be composedof plastic materials. In some embodiments, the refractive lens elementsmay be composed of injection molded optical plastic materials. However,other suitable transparent materials may be used. Also note that, in agiven embodiment, different ones of the lens elements may be composed ofmaterials with different optical characteristics, for example differentAbbe numbers and/or different refractive indices.

In embodiments of the compact lens system, the lens element materialsmay be selected and the refractive power distribution of the lenselements may be calculated to satisfy a lens system effective focallength and F-number requirement and to correct for lens artifacts andeffects including one or more of but not limited to vignetting,chromatic aberrations, lens flare, and the field curvature or Petzvalsum. For example, monochromatic and chromatic variations of opticalaberrations may be reduced by adjusting the radii of curvature andaspheric coefficients or geometrical shapes of the lens elements andaxial separations to produce well-corrected and balanced minimalresidual aberrations, as well as to reduce the total track length (TTL)and to achieve quality optical performance and high image resolution ina small form factor narrow angle camera.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional illustration of a prior art compact cameraincluding a compact lens system that includes five lens elements and anaperture stop at or in front of the front vertex of the lens system.

FIG. 2 is a cross-sectional illustration of an example embodiment of acompact camera including a compact lens system that includes six lenselements in which the aperture stop is located at the first lens elementand behind the front vertex of the lens system.

FIG. 3 is a cross-sectional illustration of an example embodiment of acompact camera including a compact lens system that includes six lenselements with refractive power in which the aperture stop is locatedbetween the first and second lens elements.

FIG. 4 is a cross-sectional illustration of another example embodimentof a compact camera including a compact lens system that includes sixlens elements with refractive power in which the aperture stop islocated between the first and second lens elements.

FIG. 5 is a flowchart of a method for capturing images using a camera asillustrated in FIG. 2, according to some embodiments.

FIG. 6 is a flowchart of a method for capturing images using a camera asillustrated in FIGS. 3 and 4, according to some embodiments.

FIG. 7 illustrates an example computer system that may be used inembodiments.

This specification includes references to “one embodiment” or “anembodiment.” The appearances of the phrases “in one embodiment” or “inan embodiment” do not necessarily refer to the same embodiment.Particular features, structures, or characteristics may be combined inany suitable manner consistent with this disclosure.

“Comprising.” This term is open-ended. As used in the appended claims,this term does not foreclose additional structure or steps. Consider aclaim that recites: “An apparatus comprising one or more processor units. . . ”. Such a claim does not foreclose the apparatus from includingadditional components (e.g., a network interface unit, graphicscircuitry, etc.).

“Configured To.” Various units, circuits, or other components may bedescribed or claimed as “configured to” perform a task or tasks. In suchcontexts, “configured to” is used to connote structure by indicatingthat the units/circuits/components include structure (e.g., circuitry)that performs those task or tasks during operation. As such, theunit/circuit/component can be said to be configured to perform the taskeven when the specified unit/circuit/component is not currentlyoperational (e.g., is not on). The units/circuits/components used withthe “configured to” language include hardware—for example, circuits,memory storing program instructions executable to implement theoperation, etc. Reciting that a unit/circuit/component is “configuredto” perform one or more tasks is expressly intended not to invoke 35U.S.C. § 112, sixth paragraph, for that unit/circuit/component.Additionally, “configured to” can include generic structure (e.g.,generic circuitry) that is manipulated by software and/or firmware(e.g., an FPGA or a general-purpose processor executing software) tooperate in manner that is capable of performing the task(s) at issue.“Configure to” may also include adapting a manufacturing process (e.g.,a semiconductor fabrication facility) to fabricate devices (e.g.,integrated circuits) that are adapted to implement or perform one ormore tasks.

“First,” “Second,” etc. As used herein, these terms are used as labelsfor nouns that they precede, and do not imply any type of ordering(e.g., spatial, temporal, logical, etc.). For example, a buffer circuitmay be described herein as performing write operations for “first” and“second” values. The terms “first” and “second” do not necessarily implythat the first value must be written before the second value.

“Based On.” As used herein, this term is used to describe one or morefactors that affect a determination. This term does not forecloseadditional factors that may affect a determination. That is, adetermination may be solely based on those factors or based, at least inpart, on those factors. Consider the phrase “determine A based on B.”While in this case, B is a factor that affects the determination of A,such a phrase does not foreclose the determination of A from also beingbased on C. In other instances, A may be determined based solely on B.

DETAILED DESCRIPTION

Embodiments of a small form factor camera including a photosensor and acompact lens system are described. Various embodiments of a compact,narrow angle lens system including six lens elements are described thatmay be used in the camera and that provide a lower F-number and shortertotal track length than has been realized in conventional compactcameras. The camera may be implemented in a small package size whilestill capturing sharp, high-resolution images, making embodiments of thecamera suitable for use in small and/or mobile multipurpose devices suchas cell phones, smartphones, pad or tablet computing devices, laptop,netbook, notebook, subnotebook, and ultrabook computers, and so on.However, note that aspects of the camera (e.g., the lens system andphotosensor) may be scaled up or down to provide cameras with larger orsmaller package sizes. In addition, embodiments of the camera system maybe implemented as stand-alone digital cameras. In addition to still(single frame capture) camera applications, embodiments of the camerasystem may be adapted for use in video camera applications.

FIG. 1 is a cross-sectional illustration of an example compact cameraincluding a compact narrow angle lens system that includes five lenselements and an aperture stop at or in front of the front vertex of thelens system. A camera 10 includes at least a compact narrow-angle lenssystem 11 and a photosensor 12. The camera 10 may include an aperturestop 30 at or in front of the front vertex of the lens system 11. Thecamera 10 may also include an infrared (IR) filter located between thelens system 11 and the photosensor 12. The compact lens system 11 ofcamera 10 may include five lens elements (21-25) with refractive powerand lens system effective focal length f, arranged along an optical axisin order from an object side to an image side:

-   -   a first lens element 21 with positive refractive power;    -   a second lens element 22 with negative refractive power;    -   a third lens element 23 with negative refractive power;    -   a fourth lens element 24 with negative refractive power; and    -   a fifth lens element 25 with positive refractive power.

The narrow-angle, five lens element lens system 11 of FIG. 1 may providean F-number (focal ratio) of 2.8 or higher. The F-number or focal ratioof a lens system is the ratio (f/D) of the lens system's focal length(f) to the diameter of the entrance pupil (D) of the aperture stop. Toachieve lower F-numbers with camera 10, the aperture of the camera 10needs to be enlarged. However, with a larger aperture, the five lenselement lens system 11 would need to be stronger (in optical power) toavoid imaging quality degradation and to achieve satisfactoryperformance. With the five lens element lens system 11 as shown in FIG.1, the total track length (TTL) of the lens system 11 would need to beincreased to increase the strength of the lens system 11. (TTL of a lenssystem is the distance from the front vertex of the lens system to theimage plane at the surface of the sensor). However, increasing the TTLof the lens system 11 increases the package size of the lens system 11,and may require the camera 10 to be larger. In addition, with theaperture stop 30 at the front vertex of the lens system 11 as shown inFIG. 1, the principal point 40 of the camera 10 is effectively at thestop 30.

Embodiments of compact narrow angle lens systems with six lens elementsare described. Embodiments may provide a larger aperture and thus lowerF-numbers when compared to five lens element lens systems. Embodimentsof the compact narrow angle lens systems with six lens elements asdescribed herein may provide higher imaging quality at lower F-numbers(e.g., at or below 2.8, for example 2.6 or 2.4) than can be achievedwith five lens element lens systems as shown in FIG. 1, while providingthe same or similar TTL and thus the same or similar package size. Thesix lens elements of the lens system provide increased optical powerwhen compared to the five-lens system 11 as illustrated in FIG. 1 toachieve satisfactory performance with the larger aperture and lowerF-numbers without increasing TTL and package size of the compact lenssystem.

In addition to the addition of a sixth lens element to the lens system,the power order of the lenses in the six lens element lens system may bedifferent than the power order of the lenses in the five lens elementlens system 11. For example, in the example five lens element lenssystem 11 of FIG. 1, the power order, from the first lens to the fifthlens, is PNNNP where P indicates a lens with positive refractive power,and N represents a lens with negative refractive power. The power orderin an example six lens element lens system as shown in FIGS. 2 through 4may be PNPNNP. Note, however, that other power orders are possible andcontemplated, for example PNPNPP or PNNNPP. In addition, in someembodiments, the location of the aperture stop may be moved behind thefront vertex of the lens system, for example behind the front vertex atthe first lens element or between the first and second lens elements.Moving the aperture stop inwards (towards the image side) effectivelymoves the ideal principal point of the camera forwards, to the objectside and in front of the front vertex of the lens system.

In addition, lens system parameters including but not limited to lensshape, geometry, position, and materials may be selected at least inpart to reduce, compensate, or correct for lens artifacts and effectsincluding one or more of but not limited to vignetting, chromaticaberration, the field curvature or Petzval sum, and lens flare. Forexample, in some embodiments, lens system parameters of one or more ofthe lens elements may be selected to adjust the light rays passingthrough the lens system to reduce or eliminate lens flare. Thus, the sixlens element lens system may reduce lens flare to produce less lensflare effect in captured images than is typically present in imagescaptured with a five lens element lens system as illustrated in FIG. 1.

Several non-limiting example embodiments of compact narrow angle lenssystems with six lens elements are described. FIG. 2 shows an exampleembodiment that includes six refracting lens elements in which theaperture stop is located at the first lens element and behind the frontvertex of the lens system. FIGS. 3 and 4 show example embodiments thatinclude six refracting lens elements in which the aperture stop islocated between the first and second lens elements. The exampleembodiments of compact narrow angle lens systems with six lens elementsas described herein may provide f-numbers that are less than 2.8, forexample 2.6, 2.4, or lower, with focal length (f) of about 6.6 mm, and aTTL of about 5.9 to 6 mm. Note, however, that these examples are notintended to be limiting, and that variations on the various parametersgiven for the lens systems are possible while still achieving similarresults.

The refractive lens elements in the various embodiments may, forexample, be composed of a plastic material. In some embodiments, therefractive lens elements may be composed of an injection molded plasticmaterial. However, other transparent materials may be used. Also notethat, in a given embodiment, different ones of the lens elements may becomposed of materials with different optical characteristics, forexample different Abbe numbers and/or different refractive indices. TheAbbe number, V_(d), may be defined by the equation:V _(d)=(N _(d)−1)/(N _(F) −N _(C)),where N_(F) and N_(C) are the refractive index values of the material atthe F and C lines of hydrogen, respectively.Small Form Factor Cameras with Low F-Number Narrow Angle Lens Systems

In each of FIGS. 2 through 4, an example camera includes at least acompact narrow-angle lens system and a photosensor. The photosensor maybe an integrated circuit (IC) technology chip or chips implementedaccording to any of various types of photosensor technology. Examples ofphotosensor technology that may be used are charge-coupled device (CCD)technology and complementary metal-oxide-semiconductor (CMOS)technology. In some embodiments, pixel size of the photosensor may be1.2 microns or less, although larger pixel sizes may be used. In anon-limiting example embodiment, the photosensor may be manufacturedaccording to a 1280×720 pixel image format to capture 1 megapixelimages. However, other pixel formats may be used in embodiments, forexample 5 megapixel, 10 megapixel, or larger or smaller formats.

The camera may also include an aperture stop (AS) located at the firstlens element and behind the front vertex of the lens system as shown inFIG. 2, or between the first and second lens elements as shown in FIGS.3 and 4.

The camera may also, but does not necessarily, include an infrared (IR)filter located between the last or sixth lens element of the lens systemand the photosensor. The IR filter may, for example, be composed of aglass material. However, other materials may be used. In someembodiments, the IR filter does not have refractive power, and does notaffect the effective focal length f of the lens system. Further notethat the camera may also include other components than those illustratedand described herein.

In the camera, the lens system forms an image at an image plane (IP) ator near the surface of the photosensor. The image size for a distantobject is directly proportional to the effective focal length f of alens system. The total track length (TTL) of the lens system is thedistance on the optical axis (AX) between the front vertex at the objectside surface of the first (object side) lens element and the imageplane. For a telephoto lens system, the total track length (TTL) is lessthan the lens system effective focal length (f), and the ratio of totaltrack length to focal length (TTL/f) is the telephoto ratio. To beclassified as a telephoto lens system, TTL/f is less than or equal to 1.For a non-telephoto lens system, the telephoto ratio is greater than 1.

In some embodiments, the lens system may be a fixed lens systemconfigured such that the effective focal length f of the lens system isat or about 6.6 millimeters (mm) (e.g., within a range of 6.0-7.0 mm),the F-number (focal ratio, or f/#) is within a range from about 2.2 toabout 2.8, the field of view (FOV) is at or about 36 degrees (althoughnarrower or wider FOVs may be achieved), and the total track length(TTL) of the lens system is within a range of about 5.5 to about 6.5 mm.

In the non-limiting example embodiments described herein (see FIGS. 2through 4), the lens system may be configured such that the effectivefocal length f of the lens system is at or about 6.6 mm. Thenon-limiting example embodiments shown in FIGS. 2 and 3 may beconfigured such that the F-number is at or about 2.6. The non-limitingexample embodiment shown in FIG. 4 may be configured such that theF-number is at or about 2.4. The lens system may, for example, beconfigured with a focal length f of 6.6 mm, TTL of 6 mm, and F-number of2.4 or 2.6 as shown in the examples to satisfy specified optical,imaging, and/or packaging constraints for particular camera systemapplications. Note that the F-number, also referred to as the focalratio or f/#, is defined by f/D, where D is the diameter of the entrancepupil, i.e. the effective aperture. As an example, at f=6.6 mm, anF-number of 2.6 is achieved with an effective aperture of @2.54 mm. Asanother example, at f=6.6 mm, an F-number of 2.4 is achieved with aneffective aperture of @2.75 mm. The example embodiment may, for example,be configured with a field of view (FOV) at or about 36 degrees. Totaltrack length (TTL) of the example embodiments may be at or about 5.9 mmor 6 mm. Telephoto ratio (TTL/f) of the example embodiments is thusabout 0.89-0.91.

However, note that the focal length f, F-number, TTL, aperture stoplocation, and/or other parameters may be scaled or adjusted to meetvarious specifications of optical, imaging, and/or packaging constraintsfor other camera system applications. Constraints for a camera systemthat may be specified as requirements for particular camera systemapplications and/or that may be varied for different camera systemapplications include but are not limited to the focal length f,effective aperture, aperture stop location, F-number, field of view(FOV), telephoto ratio, imaging performance requirements, and packagingvolume or size constraints.

In some embodiments, the lens system may be adjustable. For example, insome embodiments, a lens system as described herein may be equipped withan adjustable iris (entrance pupil) or aperture stop. Using anadjustable aperture stop, the F-number (focal ratio, or f/#) may bedynamically varied within a range. For example, if the lens system iswell corrected at f/2.6, at a given focal length f and FOV, then thefocal ratio may be varied within the range of 2.4 to 10 (or higher) byadjusting the aperture stop assuming that the aperture stop can beadjusted to the F-number setting. In some embodiments, the lens systemmay be used at faster focal ratios (<2.4) by adjusting the aperture stopat the same FOV (e.g. 36 degrees), possibly with degraded imagingquality performance, or with reasonably good performance at a smallerFOV.

While ranges of values may be given herein as examples for adjustablecameras and lens systems in which one or more optical parameters may bedynamically varied (e.g., using an adjustable aperture stop),embodiments of camera systems that include fixed (non-adjustable) lenssystems in which values for optical and other parameters are withinthese ranges may be implemented.

Referring first to embodiments as illustrated in FIG. 1, an examplecamera 100 includes at least a compact narrow-angle lens system 110 anda photosensor 120. The camera 100 may include an aperture stop 130 atthe first lens element and behind the front vertex of the lens system110. The camera 100 may also, but does not necessarily, include aninfrared (IR) filter, for example located between the lens system 110and the photosensor 120. The IR filter may act to block infraredradiation that could damage or adversely affect the photosensor, and maybe configured so as to have no effect on f.

A compact lens system 110 of a camera 100 may include six lens elements(101-106 in lens system 110 of FIG. 1) with refractive power and lenssystem effective focal length f , arranged along an optical axis AX inorder from an object side to an image side:

-   -   a first lens element L1 (101) with positive refractive power        having a convex object side surface;    -   a second lens element L2 (102) with negative refractive power        having a concave image side surface;    -   a third lens element L3 (103) with positive refractive power;    -   a fourth lens element L4 (104) with negative refractive power        having a concave object side surface;    -   a fifth lens element L5 (105) with negative refractive power        having a concave object side surface; and    -   a sixth lens element L6 (106) with positive refractive power        having a convex image side surface.        In addition, at least one of the object side and image side        surfaces of the six lens elements may be aspheric.

In some embodiments of lens system 110, L1, L3, and/or L6 may bebiconvex in shape. In some embodiments of lens system 110, L2, L4,and/or L5 may be negative meniscus lenses or biconcave lenses. However,other lens shapes may be used in lens system 110. For example, L1 may bea convex lens with a substantially flat image side surface. As anotherexample, L4 may be a concave lens with a substantially flat image sidesurface. In addition, lenses with other powers may be used. For example,L3 may have negative refractive power, and/or L5 may have positiverefractive power. In some embodiments, L3 and/or L5 have low refractivepower.

In some embodiments as illustrated in FIG. 2, one or more lens elementsmay be composed of a material (e.g., a plastic material) having an Abbenumber of V1. One or more other lens elements may be composed of amaterial (e.g., a plastic material) having an Abbe number of V2. In someembodiments, the Abbe numbers of the lens materials for the lenselements may satisfy the condition,30<V1−V2<35.

In the camera 100 of FIG. 2, the aperture stop 130 is located at thefirst lens element 101 and behind the front vertex of the lens system110. The ideal principal plane 140 is positioned in front of the frontvertex of the lens system 110, for example about 0.6 mm in front of thefront vertex. The lens system 110 may have an effective focal length fof about 6.6 mm, a TTL of about 6 mm, and an effective aperture of about2.54 mm. The F-number of the camera 100 is thus about 2.6.

Referring now to embodiments as illustrated in FIG. 3, an example camera200 includes at least a compact narrow-angle lens system 210 and aphotosensor 220. The camera 200 may include an aperture stop 230 locatedbetween the first lens element and the second lens element of the lenssystem 210. The camera 200 may also, but does not necessarily, includean infrared (IR) filter, for example located between the lens system 210and the photosensor 220. The IR filter may act to block infraredradiation that could damage or adversely affect the photosensor, and maybe configured so as to have no effect on f.

A compact lens system 210 of a camera 200 may include six lens elements(201-206) with refractive power and lens system effective focal lengthf, arranged along an optical axis AX in order from an object side to animage side:

-   -   a first lens element L1 (201) with positive refractive power        having a convex object side surface;    -   a second lens element L2 (202) with negative refractive power        having a concave image side surface;    -   a third lens element L3 (203) with positive refractive power;    -   a fourth lens element L4 (204) with negative refractive power        having a concave object side surface;    -   a fifth lens element L5 (205) with negative refractive power        having a concave object side surface; and    -   a sixth lens element L6 (206) with positive refractive power        having a convex image side surface.        In addition, at least one of the object side and image side        surfaces of the six lens elements may be aspheric.

In some embodiments of lens system 210, L1 and L3 may be biconvex inshape. In some embodiments of lens system 210, L2, L4, and/or L5 may benegative meniscus lenses or biconcave lenses. In some embodiments oflens system 210, L6 may be a positive meniscus lens. However, other lensshapes may be used in lens system 210. For example, L1 may be a convexlens with a substantially flat image side surface. As another example,L4 may be a concave lens with a substantially flat image side surface.In addition, lenses with other powers may be used. For example, L3 mayhave negative refractive power, and/or L5 may have positive refractingpower. In some embodiments, L3 and/or L5 have low refractive power.

In some embodiments as illustrated in FIG. 3, one or more lens elementsmay be composed of a material (e.g., a plastic material) having an Abbenumber of V1. One or more other lens elements may be composed of amaterial (e.g., a plastic material) having an Abbe number of V2. In someembodiments, the Abbe numbers of the lens materials for the lenselements may satisfy the condition,30<V1−V2<35.

In the camera 200 of FIG. 3, the aperture stop 230 is located betweenthe first lens element 201 and the second lens element 201 of the lenssystem 210. The ideal principal plane 240 is positioned in front of thefront vertex of the lens system 210, for example about 0.6 mm in frontof the front vertex. The lens system 210 may have an effective focallength f of about 6.6 mm, a TTL of about 6 mm, and an effective apertureof about 2.54 mm. The F-number of the camera 200 is thus about 2.6.

Referring now to embodiments as illustrated in FIG. 4, an example camera300 includes at least a compact narrow-angle lens system 310 and aphotosensor 320. The camera 300 may include an aperture stop 330 locatedbetween the first lens element and the second lens element of the lenssystem 310. The camera 300 may also, but does not necessarily, includean infrared (IR) filter, for example located between the lens system 310and the photosensor 320. The IR filter may act to block infraredradiation that could damage or adversely affect the photosensor, and maybe configured so as to have no effect on f.

A compact lens system 310 of a camera 300 may include six lens elements(301-306) with refractive power and lens system effective focal lengthf, arranged along an optical axis AX in order from an object side to animage side:

-   -   a first lens element L1 (301) with positive refractive power        having a convex object side surface;    -   a second lens element L2 (302) with negative refractive power        having a concave image side surface;    -   a third lens element L3 (303) with positive refractive power;    -   a fourth lens element L4 (304) with negative refractive power        having a concave object side surface;    -   a fifth lens element L5 (305) with negative refractive power        having a concave object side surface; and    -   a sixth lens element L6 (306) with positive refractive power        having a convex image side surface.        In addition, at least one of the object side and image side        surfaces of the six lens elements may be aspheric.

In some embodiments of lens system 310, L1 and L3 may be biconvex inshape. In some embodiments of lens system 310, L2, L4, and/or L5 may benegative meniscus lenses or biconcave lenses. In some embodiments oflens system 310, L6 may be a positive meniscus lens. However, other lensshapes may be used in lens system 310. For example, L1 may be a convexlens with a substantially flat image side surface. As another example,L4 may be a concave lens with a substantially flat image side surface.In addition, lenses with other powers may be used. For example, L3 mayhave negative refractive power, and/or L5 may have positive refractingpower. In some embodiments, L3 and/or L5 have low refractive power.

In some embodiments as illustrated in FIG. 4, one or more lens elementsmay be composed of a material (e.g., a plastic material) having an Abbenumber of V1. One or more other lens elements may be composed of amaterial (e.g., a plastic material) having an Abbe number of V2. In someembodiments, the Abbe numbers of the lens materials for the lenselements may satisfy the condition,30<V1−V2<35.

In the camera 300 of FIG. 4, the aperture stop 330 is located betweenthe first lens element 301 and the second lens element 301 of the lenssystem 310. The ideal principal plane 340 is positioned in front of thefront vertex of the lens system 310, for example about 0.6 mm in frontof the front vertex. The lens system 310 may have an effective focallength f of about 6.6 mm, a TTL of about 6 mm, and an effective apertureof about 2.75 mm. The F-number of the camera 300 is thus about 2.4.

FIG. 5 is a high-level flowchart of a method for capturing images usinga camera with a lens system that includes six lens elements and anaperture stop at the first lens element and behind the front vertex ofthe lens system as illustrated in FIGS. 2 and 3, according to someembodiments. As indicated at 1100, light from an object field in frontof the camera is received at a first lens element of the camera throughan aperture stop. In some embodiments, the aperture stop may be locatedat the first lens element and behind the front vertex of the lenssystem. As indicated at 1102, the first lens element refracts the lightto a second lens element. In some embodiments, the first lens elementmay have positive refracting power. As indicated at 1104, the light isthen refracted by the second lens element to a third lens element. Insome embodiments, the second lens element may have negative refractingpower. As indicated at 1106, the light is then refracted by the thirdlens element to a fourth lens element. In some embodiments, the thirdlens element may have positive refracting power. As indicated at 1108,the light is then refracted by the fourth lens element to a fifth lenselement. In some embodiments, the fourth lens element may have negativerefracting power. As indicated at 1110, the light is then refracted bythe fifth lens element to a sixth lens element. In some embodiments, thefifth lens element may have negative refracting power. As indicated at1112, the light is refracted by the sixth lens element to form an imageat an image plane at or near the surface of a photosensor. In someembodiments, the sixth lens element may have positive refracting power.As indicated at 1114, the image is captured by the photosensor. Whilenot shown, in some embodiments, the light may pass through an infraredfilter that may for example be located between the sixth lens elementand the photosensor.

In some embodiments, the six lens elements referred to in FIG. 5 may beconfigured as illustrated in FIG. 2. Alternatively, the six lenselements may be configured as illustrated in FIG. 3. However, note thatvariations on the examples given in FIGS. 2 and 3 are possible whileachieving similar optical results.

FIG. 6 is a high-level flowchart of a method for capturing images usinga camera with a lens system that includes six lens elements and anaperture stop at the first lens element and behind the front vertex ofthe lens system as illustrated in FIG. 4, according to some embodiments.As indicated at 1200, light from an object field in front of the camerais received at a first lens element of the camera. As indicated at 1202,the first lens element refracts the light through an aperture stop to asecond lens element. In some embodiments, the aperture stop may belocated between the first lens element and the second lens element ofthe lens system. In some embodiments, the first lens element may havepositive refracting power. As indicated at 1204, the light is thenrefracted by the second lens element to a third lens element. In someembodiments, the second lens element may have negative refracting power.As indicated at 1206, the light is then refracted by the third lenselement to a fourth lens element. In some embodiments, the third lenselement may have positive refracting power. As indicated at 1208, thelight is then refracted by the fourth lens element to a fifth lenselement. In some embodiments, the fourth lens element may have negativerefracting power. As indicated at 1210, the light is then refracted bythe fifth lens element to a sixth lens element. In some embodiments, thefifth lens element may have negative refracting power. As indicated at1212, the light is refracted by the sixth lens element to form an imageat an image plane at or near the surface of a photosensor. In someembodiments, the sixth lens element may have positive refracting power.As indicated at 1214, the image is captured by the photosensor. Whilenot shown, in some embodiments, the light may pass through an infraredfilter that may for example be located between the sixth lens elementand the photosensor.

In some embodiments, the six lens elements referred to in FIG. 6 may beconfigured as illustrated in FIG. 4. However, note that variations onthe example given in FIG. 4 are possible while achieving similar opticalresults.

Example Computing Device

FIG. 7 illustrates an example computing device, referred to as computersystem 2000, that may include or host embodiments of the camera asillustrated in FIGS. 2 through 6. In addition, computer system 2000 mayimplement methods for controlling operations of the camera and/or forperforming image processing of images captured with the camera. Indifferent embodiments, computer system 2000 may be any of various typesof devices, including, but not limited to, a personal computer system,desktop computer, laptop, notebook, tablet or pad device, slate, ornetbook computer, mainframe computer system, handheld computer,workstation, network computer, a camera, a set top box, a mobile device,a wireless phone, a smartphone, a consumer device, video game console,handheld video game device, application server, storage device, atelevision, a video recording device, a peripheral device such as aswitch, modem, router, or in general any type of computing or electronicdevice.

In the illustrated embodiment, computer system 2000 includes one or moreprocessors 2010 coupled to a system memory 2020 via an input/output(I/O) interface 2030. Computer system 2000 further includes a networkinterface 2040 coupled to I/O interface 2030, and one or moreinput/output devices 2050, such as cursor control device 2060, keyboard2070, and display(s) 2080. Computer system 2000 may also include one ormore cameras 2090, for example one or more cameras as described abovewith respect to FIGS. 2 through 6, which may also be coupled to I/Ointerface 2030, or one or more cameras as described above with respectto FIGS. 2 through 6 along with one or more other cameras such asconventional wide-field cameras.

In various embodiments, computer system 2000 may be a uniprocessorsystem including one processor 2010, or a multiprocessor systemincluding several processors 2010 (e.g., two, four, eight, or anothersuitable number). Processors 2010 may be any suitable processor capableof executing instructions. For example, in various embodimentsprocessors 2010 may be general-purpose or embedded processorsimplementing any of a variety of instruction set architectures (ISAs),such as the x86, PowerPC, SPARC, or MIPS ISAs, or any other suitableISA. In multiprocessor systems, each of processors 2010 may commonly,but not necessarily, implement the same ISA.

System memory 2020 may be configured to store program instructions 2022and/or data 2032 accessible by processor 2010. In various embodiments,system memory 2020 may be implemented using any suitable memorytechnology, such as static random access memory (SRAM), synchronousdynamic RAM (SDRAM), nonvolatile/Flash-type memory, or any other type ofmemory. In the illustrated embodiment, program instructions 2022 may beconfigured to implement various interfaces, methods and/or data forcontrolling operations of camera 2090 and for capturing and processingimages with integrated camera 2090 or other methods or data, for exampleinterfaces and methods for capturing, displaying, processing, andstoring images captured with camera 2090. In some embodiments, programinstructions and/or data may be received, sent or stored upon differenttypes of computer-accessible media or on similar media separate fromsystem memory 2020 or computer system 2000.

In one embodiment, I/O interface 2030 may be configured to coordinateI/O traffic between processor 2010, system memory 2020, and anyperipheral devices in the device, including network interface 2040 orother peripheral interfaces, such as input/output devices 2050. In someembodiments, I/O interface 2030 may perform any necessary protocol,timing or other data transformations to convert data signals from onecomponent (e.g., system memory 2020) into a format suitable for use byanother component (e.g., processor 2010). In some embodiments, I/Ointerface 2030 may include support for devices attached through varioustypes of peripheral buses, such as a variant of the Peripheral ComponentInterconnect (PCI) bus standard or the Universal Serial Bus (USB)standard, for example. In some embodiments, the function of I/Ointerface 2030 may be split into two or more separate components, suchas a north bridge and a south bridge, for example. Also, in someembodiments some or all of the functionality of I/O interface 2030, suchas an interface to system memory 2020, may be incorporated directly intoprocessor 2010.

Network interface 2040 may be configured to allow data to be exchangedbetween computer system 2000 and other devices attached to a network2085 (e.g., carrier or agent devices) or between nodes of computersystem 2000. Network 2085 may in various embodiments include one or morenetworks including but not limited to Local Area Networks (LANs) (e.g.,an Ethernet or corporate network), Wide Area Networks (WANs) (e.g., theInternet), wireless data networks, some other electronic data network,or some combination thereof. In various embodiments, network interface2040 may support communication via wired or wireless general datanetworks, such as any suitable type of Ethernet network, for example;via telecommunications/telephony networks such as analog voice networksor digital fiber communications networks; via storage area networks suchas Fibre Channel SANs, or via any other suitable type of network and/orprotocol.

Input/output devices 2050 may, in some embodiments, include one or moredisplay terminals, keyboards, keypads, touchpads, scanning devices,voice or optical recognition devices, or any other devices suitable forentering or accessing data by computer system 2000. Multipleinput/output devices 2050 may be present in computer system 2000 or maybe distributed on various nodes of computer system 2000. In someembodiments, similar input/output devices may be separate from computersystem 2000 and may interact with one or more nodes of computer system2000 through a wired or wireless connection, such as over networkinterface 2040.

As shown in FIG. 17, memory 2020 may include program instructions 2022,which may be processor-executable to implement any element or action tosupport integrated camera 2090, including but not limited to imageprocessing software and interface software for controlling camera 2090.In some embodiments, images captured by camera 2090 may be stored tomemory 2020. In addition, metadata for images captured by camera 2090may be stored to memory 2020.

Those skilled in the art will appreciate that computer system 2000 ismerely illustrative and is not intended to limit the scope ofembodiments. In particular, the computer system and devices may includeany combination of hardware or software that can perform the indicatedfunctions, including computers, network devices, Internet appliances,PDAs, wireless phones, pagers, video or still cameras, etc. Computersystem 2000 may also be connected to other devices that are notillustrated, or instead may operate as a stand-alone system. Inaddition, the functionality provided by the illustrated components mayin some embodiments be combined in fewer components or distributed inadditional components. Similarly, in some embodiments, the functionalityof some of the illustrated components may not be provided and/or otheradditional functionality may be available.

Those skilled in the art will also appreciate that, while various itemsare illustrated as being stored in memory or on storage while beingused, these items or portions of them may be transferred between memoryand other storage devices for purposes of memory management and dataintegrity. Alternatively, in other embodiments some or all of thesoftware components may execute in memory on another device andcommunicate with the illustrated computer system 2000 via inter-computercommunication. Some or all of the system components or data structuresmay also be stored (e.g., as instructions or structured data) on acomputer-accessible medium or a portable article to be read by anappropriate drive, various examples of which are described above. Insome embodiments, instructions stored on a computer-accessible mediumseparate from computer system 2000 may be transmitted to computer system2000 via transmission media or signals such as electrical,electromagnetic, or digital signals, conveyed via a communication mediumsuch as a network and/or a wireless link. Various embodiments mayfurther include receiving, sending or storing instructions and/or dataimplemented in accordance with the foregoing description upon acomputer-accessible medium. Generally speaking, a computer-accessiblemedium may include a non-transitory, computer-readable storage medium ormemory medium such as magnetic or optical media, e.g., disk orDVD/CD-ROM, volatile or non-volatile media such as RAM (e.g. SDRAM, DDR,RDRAM, SRAM, etc.), ROM, etc. In some embodiments, a computer-accessiblemedium may include transmission media or signals such as electrical,electromagnetic, or digital signals, conveyed via a communication mediumsuch as network and/or a wireless link.

The methods described herein may be implemented in software, hardware,or a combination thereof, in different embodiments. In addition, theorder of the blocks of the methods may be changed, and various elementsmay be added, reordered, combined, omitted, modified, etc. Variousmodifications and changes may be made as would be obvious to a personskilled in the art having the benefit of this disclosure. The variousembodiments described herein are meant to be illustrative and notlimiting. Many variations, modifications, additions, and improvementsare possible. Accordingly, plural instances may be provided forcomponents described herein as a single instance. Boundaries betweenvarious components, operations and data stores are somewhat arbitrary,and particular operations are illustrated in the context of specificillustrative configurations. Other allocations of functionality areenvisioned and may fall within the scope of claims that follow. Finally,structures and functionality presented as discrete components in theexample configurations may be implemented as a combined structure orcomponent. These and other variations, modifications, additions, andimprovements may fall within the scope of embodiments as defined in theclaims that follow.

What is claimed is:
 1. A lens system, comprising: six refractive lenselements arranged along an optical axis and configured to refract lightfrom an object field to form an image of a scene at an image plane,wherein the lens elements include, in order along the optical axis froman object side to an image side: a first lens element with positiverefractive power having a convex object side surface; a second lenselement with negative refractive power having a concave image sidesurface and a concave object side surface; a third lens element having aconvex image side surface; a fourth lens element with negativerefractive power having a concave image side surface; a fifth lenselement; and a sixth lens element with positive refractive power havinga convex image side surface; and an aperture stop located behind a frontvertex of the lens system; wherein a total track length (TTL) of thelens system is 6.5 millimeter or less, and wherein a focal ratio of thelens system is 2.8 or less; and wherein the lens system has effectivefocal length f and wherein a telephoto ratio (TTL/f ) of the lens systemis less than or equal to 1.0.
 2. The lens system as recited in claim 1,wherein the third lens element from the object side of the lens systemis a positive lens with positive refractive power.
 3. The lens system asrecited in claim 1, wherein the fifth lens element from the object sideof the lens system is a negative lens with negative refractive power. 4.The lens system as recited in claim 1, wherein effective focal length fof the lens system is 7.0 millimeters or less.
 5. The lens system asrecited in claim 1, wherein the aperture stop is located between thefirst lens element and the second lens element of the lens system. 6.The lens system as recited in claim 1, wherein effective aperture of thelens system is 2.8 millimeters or less.
 7. A camera system, comprising:a lens system comprising: six refractive lens elements arranged along anoptical axis and configured to refract light from an object field toform an image of a scene at an image plane, wherein the six refractivelens elements include, in order along the optical axis from an objectside to an image side: a first lens element with positive refractivepower having a convex object side surface; a second lens element withnegative refractive power having a concave image side surface and aconcave object side surface; a third lens element having a convex imageside surface; a fourth lens element with negative refractive powerhaving a concave image side surface; a fifth lens element; and a sixthlens element with positive refractive power having a convex image sidesurface; and an aperture stop located behind a front vertex of the lenssystem; wherein a total track length (TTL) of the lens system is 6.5millimeter or less, and wherein a focal ratio of the lens system is 2.8or less; wherein the lens system has effective focal length f , andwherein a telephoto ratio (TTL/f ) of the lens system is less than orequal to 1.0; and a photosensor configured to capture light projectedonto a surface of the photosensor from the lens system.
 8. The camerasystem as recited in claim 7, wherein effective aperture of the lenssystem is 2.8 millimeters or less.
 9. The camera system as recited inclaim 7, wherein the third lens element from the object side is apositive lens with positive refractive power.
 10. The camera system asrecited in claim 7, wherein the fifth lens element from the object sideis a negative lens with negative refractive power.
 11. The camera systemas recited in claim 7, wherein at least one surface of at least one ofthe six refractive lens elements is aspheric.
 12. The camera system asrecited in claim 7, wherein at least one of the six refractive lenselements is composed of a first plastic material, and wherein at leastone other of the six refractive lens elements is composed of a secondplastic material with different optical characteristics than the firstplastic material.
 13. A device, comprising: one or more processors; oneor more cameras; and a memory comprising program instructions executableby at least one of the one or more processors to control operations ofthe one or more cameras; wherein at least one of the one or more camerascomprises: a photosensor configured to capture light projected onto asurface of the photosensor; and a lens system configured to refractlight from an object field located in front of the camera to form animage of a scene at an image plane proximate to the surface of thephotosensor, wherein the lens system comprises: six refractive lenselements arranged along an optical axis and configured to refract lightfrom an object field to form an image of a scene at an image plane,wherein the lens elements include, in order along the optical axis froman object side to an image side: a first lens element with positiverefractive power having a convex object side surface; a second lenselement with negative refractive power having a concave image sidesurface and a concave object side surface; a third lens element having aconvex image side surface; a fourth lens element with negativerefractive power having a concave image side surface; a fifth lenselement; and a sixth lens element with positive refractive power havinga convex image side surface; and an aperture stop located behind a frontvertex of the lens system; wherein a total track length (TTL) of thelens system is 6.5 millimeter or less, and wherein a focal ratio of thelens system is 2.8 or less; and wherein the lens system has effectivefocal length f and wherein a telephoto ratio (TTL/f ) of the lens systemis less than or equal to 1.0.
 14. The device as recited in claim 13,wherein effective aperture of the lens system is 2.8 millimeters orless.
 15. The device as recited in claim 13, wherein the third lenselement from the object side is a positive lens with positive refractivepower.
 16. The device as recited in claim 13, wherein the fifth lenselement from the object side is a negative lens with negative refractivepower.
 17. The device as recited in claim 13, wherein at least onesurface of at least one of the six refractive lens elements is aspheric.